From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f172.google.com (mail-pl1-f172.google.com [209.85.214.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E74513D8907 for ; Fri, 1 May 2026 17:25:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777656338; cv=none; b=EmRd3IduKdKr57u8gUv64FZfjwQRhyvTEdD1WjMJ060WH6rL4wciYHPajO1ybI5TW90hYewtfsKDLs+QiTvRQzvBcl3c1RdwaILuTINaPX7LUnBV+qIBXLc73mrW2vufCfSj7DrCUza9wRKeDi7sNVDTTi01jDDd7yKVGF6BIsU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777656338; c=relaxed/simple; bh=2srHf7GIl/tibrCrIcmdObSAgG7zX5V8NLa+IAsRtrg=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=CrDbtzN3GPRgOV2zmX1E27RUBfuwoK+sOeb2AdJ49ajJKaxIRcOcIv+wXkNv0bvW3fqkcrrXZyyaJLZzf8Ypy53VkfiFcwpi0HoJcX76KWqu3gsnrF91cedpR4wnN5i162jf4GgPpJGQnGNWwBK2zs5ijJIrvyjPxlZDaDc7AGw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=cS+Vbdws; arc=none smtp.client-ip=209.85.214.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="cS+Vbdws" Received: by mail-pl1-f172.google.com with SMTP id d9443c01a7336-2ad4d639db3so9595495ad.0 for ; Fri, 01 May 2026 10:25:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1777656336; x=1778261136; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=K+HMcI/9s3RPCJwI7of2kYI/MCsDHTZiRUZd9gr7WX0=; b=cS+VbdwswbDJahR2gOU4/PNfvdB22zYJ59fZNhiud+uJXXiDhyMSpqQOy9bHxm2OA3 PZhducucgU7TCY4hnyEd1lrJkNp9wTmc7UGHEVXcJWuKeBXzttrg7rkMq+T0DMy2XnLE 2RxSL36WuIEXfhT/XS4QLwv58O0AOR5SJZbzu67TDlN8INIeA3f9KLjScs7pSqgpLcG/ N9XhxEqnU9b1PqGr7YB6zdW7zbLpfNiNDmZJ23yKj26MdKiMSlg6Pb3LgLugCChoiUhk m53TT/iLINmH/NJd6RWwa2bMIdgpReJz6GLtnZwliUDsbGw1iV2NucEowbYAldffunJX 6f6Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777656336; x=1778261136; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=K+HMcI/9s3RPCJwI7of2kYI/MCsDHTZiRUZd9gr7WX0=; b=IKsxMmWZ5IGDXYxFH7wmDL039dv/8y4POt40EsKjXQ8859fJkpkydSOc8ptjsKwZMm Juw7/bzevx97M0mPpG+pRGPl2ySEXCdpYsizqBoaozSltUcPSwHnbgh6pUH3kHnX6zoq Z9YwTdJ/dxCT9ruj9iVinMlOzDqhoDwT87/Kqc8P9CBHwwDdXgXu2AIrjMzVxwXIM4Cq A1JCwdnVIKyFJD0/IMmk5qmqBvTvOpHJuBmL31XqtCkz3sy9FYiUpv4+yZoX0Q+ikNKw Bl937BZliEbjVfPYTkDR9IkcnEvx1oa6zrQAszPWnBeeMate5HRXSH2f4mBf3mhC0hI8 dEag== X-Gm-Message-State: AOJu0Yz1qoOcPL38lytXqKKsPwDi91G/TvMYZNHUn2AS3To4Rs7b2dIw GdLbUbWyrwdDLu4lpy2Zw7aOLAEjOPSZbTIPAJb0jkNbicFJ+4mrxQOg X-Gm-Gg: AeBDiesCykkvdUZO7Wkk5W4U9vpGJeusKIRjwovmbRduLJPmEDzUqGqbluG42vec0UJ 8krInGgYMkljaBn1UqVYaZXsXkNPJuDEjjGr1up/s55mxeY9CL036l+jSRzWHv28pngbID03NMO KIWRE7//PFEwGOyiZTXo4cXTwdi0AOvGI0WYOiuDk3gvk3kNt8suAFpq/IBczulm+Z8xVTuAjhU Y1om/tU08c53mN1B3dA2kfbRgzcj7U4or0Fkdp8C6wwQj/KN1k/yCZv32nqKylNe1YuL9h1kqCR L5G6jWWo02M8rEcILq4G/f3bFhXTy3T0qrLR4cmIxeuoWsSaRJlFQuNA+msHK4tZlElIW2yx4KH GztwvSXAIGibLFbehIzTxdSNWp9jlcd7uDvtibVGz6fVlSRQZIeheuCfQGw8QJO5dVJk/c9UhQg r5ZG5GVL+BDo8ksiZwLo4LjGTiPMihGdrSNaM4NgE= X-Received: by 2002:a17:902:db10:b0:2b9:ee49:29d9 with SMTP id d9443c01a7336-2b9f25fd090mr1599795ad.29.1777656336150; Fri, 01 May 2026 10:25:36 -0700 (PDT) Received: from vini ([2401:4900:8fcb:edbd:7155:edb6:dac:107e]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b9caab231dsm28800675ad.26.2026.05.01.10.25.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 01 May 2026 10:25:35 -0700 (PDT) From: Vineet Agarwal To: tytso@mit.edu Cc: linux-ext4@vger.kernel.org, adilger.kernel@dilger.ca, libaokun@linux.alibaba.com, jack@suse.cz, ojaswin@linux.ibm.com, ritesh.list@gmail.com, yi.zhang@huawei.com, linux-kernel@vger.kernel.org, Vineet Agarwal Subject: [RFC] ext4: possible inconsistency in ext4_append() error path Date: Fri, 1 May 2026 22:55:06 +0530 Message-ID: <20260501172506.563064-1-agarwal.vineet2006@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi, While looking into ext4 directory operations, I noticed a possible inconsistency in the error handling of ext4_append(). In ext4_append(), the inode size is updated before all failure points have been ruled out: bh = ext4_bread(handle, inode, *block, EXT4_GET_BLOCKS_CREATE); if (IS_ERR(bh)) return bh; inode->i_size += inode->i_sb->s_blocksize; EXT4_I(inode)->i_disksize = inode->i_size; err = ext4_mark_inode_dirty(handle, inode); if (err) goto out; err = ext4_journal_get_write_access(handle, inode->i_sb, bh, EXT4_JTR_NONE); if (err) goto out; If either ext4_mark_inode_dirty() or ext4_journal_get_write_access() fails, the function returns an error but does not restore the original inode size. Callers of ext4_append() appear to treat it as an all-or-nothing operation: bh = ext4_append(handle, dir, &block); if (IS_ERR(bh)) goto out; However, in the failure case, inode->i_size may already have been increased. One possible consequence is that subsequent checks relying on i_size, such as: if (block >= inode->i_size >> inode->i_blkbits) may allow a block index to pass bounds checks even though the append operation did not complete successfully. I understand that journaling may ensure on-disk consistency, but the in-memory inode state may still temporarily reflect a change that did not logically succeed. Is this behavior intentional, or should ext4_append() avoid updating i_size until after all failure points, or roll it back on error? Thanks, Vineet Agarwal